1. Field of the Invention
This invention relates to propellants. Particularly, this invention relates to gun propellants. More particularly, this invention relates to hybrid gun propellants. In still greater particularity, this invention relates to hybrid gun propellants containing a liquid oxidizer rich monopropellant and an oxygen deficient solid propellant.
2. Description of the Prior Art
Conventional gun propellants have been from two classes either solid or liquid. Solid propellants are characteristically fuel rich which can result in muzzle flash from unburned fuel when a projectile exits from a gun muzzle. Excessive muzzle flash is undesirable for military guns as it can permit an enemy to locate and identify ground based gun systems.
Liquid monopropellants are characterized by difficulties in the control of their pressure/time history. Hydroxylammonium nitrate (HAN) has previously been used in conjunction with other ingredients in liquid monopropellant guns. There were problems controlling the pressure/time history which resulted in unacceptable shot to shot variations. Later, HAN was studied as an oxidizer with hydrocarbon (HC) fuels in liquid bipropellant systems. Although there were good combustion results, the volume ratio of oxidizer to fuel needed to be large. A by volume ratio exceeding 10 parts HAN to 1 part HC restricted this system.
The pressure/time history or curve produced by conventional solid propellants contains a high pressure peak. This high pressure placed stress upon the gun and caused flame erosion in the gun barrels. Additionally, the sharp peak results in acceleration loads on the projectile, which places stress on any mechanism in the projectile, i.e. fuze and guidance systems.
Additionally, the muzzle velocity is determined by the area under the pressure versus time curve. An increase in muzzle velocity over conventional gun propellant systems could be achieved by altering the pressure/time curve.
Often, it can be desirable to fire a heavier projectile. In order to fire a substantially heavier than normal projectile from a given size cartridge, other parameters must be adjusted. With a solid propellant, a heavier projectile required the use of a different propellant to moderate the peak pressure. Otherwise, the result would be a large increase in peak pressure or a much reduced muzzle velocity.